JP2015030532A - Large-size tank for chemical liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a crack when falling or a production cost, in a large-size tank for a chemical liquid assembled by joining a plurality of members.SOLUTION: A large-size tank for a chemical liquid has a body member in which a bottom face and a lid are joined to a cylindrical body part by seam welding. The downmost end of the cylindrical body part is made to be an outward curl shape, and the large-size tank for a chemical liquid uses a ferritic stainless steel added with 0.1 mass% or greater of each of Cu and Nb, or a ferritic stainless steel added with 0.3 mass% or greater of Mo and 0.1 mass% or greater of Nb, as a tank material.

Description

  The present invention relates to a large tank for chemicals made of metal, for example, a large tank for storing and transporting agricultural chemicals, pharmaceuticals, and non-aqueous electrolytes.

Conventional large tanks for chemical liquids are required to prevent leakage of the contents of chemical liquids and to have impact resistance when dropped in consideration of safety during handling.
In order to meet such a demand, Patent Document 1 discloses that a cylinder port is integrally formed at the upper part of the tank, and a lid joined with a pipe for injecting and discharging a chemical solution into the cylinder port is sealed, and deformation of the pipe is performed. In order to prevent breakage, a chemical transport container having a structure in which a cylindrical skirt is provided in the upper part of the tank is disclosed. In addition, a cylindrical skirt is provided at the bottom of the tank to make the tank with a hemispherical bottom surface stand on the floor surface so that the bottom surface of the tank directly below the pipe is the lowest so as to discharge the entire amount of chemicals as much as possible. ing.
Patent Document 2 proposes a large chemical tank made of austenitic stainless steel as a tank for storing chemicals.

Japanese Patent No. 3162329 JP-A-56-102561

Thus, the conventionally proposed large tanks for chemicals have a sufficient sealing structure to prevent chemicals from leaking, and the bottom of the tank is intended to stand on the floor surface. Although a skirt or a cup-shaped member is provided, the impact resistance strength when the tank is dropped is insufficient. This is because, in a skirt or cup-shaped member for the purpose of allowing the tank to stand on the floor (hereinafter referred to as a tank self-supporting purpose member), the bottom surface of the tank body is substantially the same height as the lower end of the tank self-supporting purpose member. Therefore, not only the self-supporting objective member of the tank receives the impact when the tank falls, but also the tank body. Therefore, it has been desired to have a structure with excellent shock absorption characteristics. In recent years, large tanks for chemicals have been frequently transported overseas, and in order to meet the United Nations Dangerous Goods Transport Recommendations and the United Nations Dangerous Goods Transport and Classification Harmonization Expert Committee, A tank structure with high impact strength is required.
In addition, since a plurality of members are TIG welded with a lap joint, it is necessary to add a process of polishing a raised weld bead and a process of sputtering treatment generated during welding, which increases production costs. There's a problem. In addition, gaps may be generated between the respective members before welding, and partial melting of the gaps is likely to occur during welding. Therefore, it is necessary to restrain each member in order to reduce the gap. . This increases the working time and the production cost.

In addition, it has been proposed to use austenitic stainless steel as a material for large chemical tanks. However, since Ni is contained, the material cost is high, so it was difficult to deploy in many applications. .
In order to solve the above-mentioned problems, an object of the present invention is to provide a large chemical tank that has high impact resistance, has corrosion resistance to the chemical solution in the contents, and is low in cost.

In order to achieve the object, the large chemical tank according to the present invention includes a cylindrical body, a hemispherical bottom plate, a lid, a main body member having a lower flange, and a pipe member that injects and discharges the chemical. The bottom end of the cylindrical body is an outwardly curled shape, and a hemispherical bottom plate and a lid are joined to the cylindrical body by seam welding.
Moreover, as a raw material of the large tank for chemical liquids, 0.3 mass% or more of Mo and ferritic stainless steel added with 0.1 mass% or more of Nb, or 0.1 mass% or more of Cu and Nb were added respectively. It is also characterized by using ferritic stainless steel.

In the large chemical tank according to the present invention, the lower end of the cylindrical body of the main body member has an outwardly curled shape. It is never opened. On the other hand, if the lower end of the lower cylindrical member is curled inward, the curl is opened by an impact when the large chemical tank is dropped. When the curl is released, deformation due to impact is concentrated only in the vicinity of the part where the curl is opened, resulting in a large deformation, and this part may lead to cracking of the tank. That is, by curling the lowermost end of the lower cylindrical member outward, the impact due to the drop is received by a wide portion of the lower cylindrical member, so that local deformation can be prevented. Thereby, the distortion propagated to the main body of the large tank for chemical liquid is relieved and cracking can be prevented.
In addition, since the hemispherical bottom plate and lid are joined to the cylindrical body by seam welding, even if a gap is created by overlapping each member, the electrode wheel is pressed during seam welding. Therefore, it is possible to prevent gaps from being generated, so that stable welding is possible and production costs can be prevented from increasing.
Further, the material of the main body member, pipe member, and cylindrical member of the large chemical tank is made of ferritic stainless steel to which Mo is added by 0.3 mass% or more and Nb is added by 0.1 mass% or more, or Cu and Nb, respectively. Since the ferritic stainless steel is added in an amount of 0.1% by mass or more, it has sufficient strength against impact caused by dropping or collision during handling, and has high corrosion resistance against the chemical solution in the contents. In addition, the cost of the large chemical tank can be reduced.

Schematic cross-sectional view of the large chemical tank of the present invention The figure which shows the corrosion resistance comparison result with salt spray test

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of a large chemical liquid tank 1 according to an embodiment of the present invention. The large chemical tank 1 is composed of a main body member 2 for storing the chemical liquid and a pipe member 12 for injecting and discharging the chemical liquid. The main body member 2 is composed of a cylindrical body 5, a hemispherical bottom surface 6, a lid 3 and a lower flange 11.
The pipe member 12 is composed of a pipe 4 that is inserted into the main body member 2 and injects and discharges the chemical liquid, and an upper flange 8. In order to seal the chemical liquid inside the main body member 2, an upper flange 8 and a lower flange are provided. The pipe 4 is inserted into the main body member 2 while sandwiching the sealing material 9 between the upper flange 8 and the lower flange 11 with a bolt 10.

The cylindrical body 5 of the main body member 2 is completed by processing the material into a cylindrical shape, joining the butted portions by welding, and processing the lowermost end into an outwardly curled shape. A bottom plate 6 processed into a hemispherical shape is assembled to one end of the body portion 5 by seam welding (welding portion 15), and the lid 3 and the lower flange 11 are joined to the other end by welding. The lid 3 is assembled by welding the circumference by seam welding (welded portion 15). The butt welding of the cylindrical body 5 and the method of welding the lower flange 11 to the lid 3 are not particularly defined, but in consideration of workability, it is preferable to use fusion welding such as TIG welding that can be welded from one side.
The cylindrical body 5 and the lid 3 are joined to prevent the pipe member 12 from being deformed or broken due to the collision of the large chemical tank 1 from the side surface. At the position surrounding In addition, the cylindrical body 5 and the semispherical bottom plate 5 are joined when the large tank 1 for chemical liquid falls in the area below the position where the cylindrical body 5 is joined to the semispherical bottom plate 6. This is performed at the position where the lower region 13 is provided so as to absorb the impact force by deformation.

The lid 3 has an insertion port 7 for inserting the pipe 4 into the main body member 2. The insertion port 7 is manufactured by drilling and burring a predetermined dimension in the center of the lid 3 and then welding the lower flange 11. The upper flange 8 is joined to the pipe 4 by welding, and is provided with bolt holes for assembling with the lower flange 11 with bolts 10.
The welding method used for joining the upper flange 8 and the pipe 4 or joining the lower flange 11 and the lid 3 is not particularly limited, but it is preferable to use fusion welding such as TIG welding that allows welding from one side in consideration of workability.

  In the present invention, a ferritic stainless steel to which a specific component is added is used for the members constituting the chemical liquid large tank 1 in consideration of the corrosion resistance against the chemical liquid, the strength performance against dropping and collision, and the cost. In particular, the corrosion resistance needs to be equal to or better than that of austenitic stainless steel. Therefore, the present inventors added a ferrite and a ferritic stainless steel to which Cu and Nb are added or Mo and Nb are added. Focused on stainless steel.

  The thermal expansion coefficient of these ferritic stainless steels is about 1/2 that of austenitic stainless steels, and the thermal conductivity is about 1.5 times and heat diffusion is fast. The deformation is also about ½ or less. In proportion to the decrease in the amount of deformation, it is possible to reduce the fastening force of the member during welding.

The corrosion resistance of these ferritic stainless steels was found to be equivalent to or higher than that of SUS304 as shown in FIG. 2 in comparison with a typical salt spray test (JIS Z 2371) with SUS304. Here, the rating number in FIG. 2 is determination of the salt spray test result evaluated based on the rating number method described in JIS Z 2371 Annex 1.
Moreover, the component composition of each test material used in this salt spray test is as shown in Table 1.

Table 1 Composition of stainless steel used for salt spray test (mass%)

Of these component compositions, Mo has the effect of improving the corrosion resistance in the presence of Cr. Further, the action of Cu is an effect of stabilizing the passive film by reducing the anode current, and the action of Nb suppresses the Cr deficiency by suppressing the precipitation of Cr carbide at the grain boundary by forming NbC. It is an effect.
As described above, by using the ferritic stainless steel of the present invention as a raw material for a large tank for chemicals, corrosion resistance equivalent to or higher than that of austenitic stainless steel can be ensured.

  In addition, as a ferritic stainless steel used as a base, C: 0.25% or less, Si: 2.0% or less, Mn: 1.0% or less, P: 0.04% or less, S: Based on 0.01% or less, Cr: 16 to 35%, N: 0.025% or less, Nb: 0.1 to 0.6%, Cu: 0.1 to 1.0%, Mo: Those containing 0.3 to 6.0% are preferred.

  C and N may be included in SUS430 or SUS434 from the viewpoint of corrosion resistance. However, when strength forming or welding is performed, workability, corrosion resistance and intergranular corrosion resistance, or toughness are required. To C and N are preferably as low as possible. On the other hand, lowering the C and N lengthens the refining time and increases the manufacturing cost. This is allowed to be included to some extent by adding an appropriate amount of Nb having an action of fixing C and N. For this reason, C is 0.25% by mass or less and N is 0.025% by mass or less. However, when workability and corrosion resistance or toughness of the welded portion are required, C is 0.03% by mass or less, N is preferably 0.02% by mass or less.

  Si has a deoxidizing action and, as will be described later, Mn having the same action is reduced from the aspect of corrosion resistance, so that a larger amount is desirable. However, if the amount is too large, the steel is hardened and the workability is impaired, and it is also harmful to hot cracking and weld toughness during welding, so the upper limit is set to 2.0% by mass.

  Mn has a strong ability to form sulfides, and forms MnS which bonds with S in steel and is unstable in an aqueous solution and easily causes rusting, and deteriorates corrosion resistance. As Mn decreases, the pitting potential becomes noble and the corrosion resistance is improved. In order to obtain significant corrosion resistance, it is necessary to make Mn 1.0% by mass or less.

S is bonded to Mn as described above, which is harmful to corrosion resistance, and is preferably low. In order to obtain significant corrosion resistance, S needs to be 0.01% by mass or less. Particularly when used under severe conditions, the content is preferably 0.002% by mass or less.

  Cr is a main constituent element of the passive film, and at least 16% by mass of Cr is required to obtain a passive effect. An increase in Cr leads to embrittlement of the steel, and is liable to cause cracks and rough skin during processing, and the softness is impaired. Further, the increase in Cr makes it difficult to manufacture and causes an increase in manufacturing cost. For these reasons, the upper limit is 35% by mass.

  Nb is known as an element that fixes C and N in steel, and is usually added to improve the workability and various properties of the weld. In addition to these effects, grain boundaries due to NbC formation are added. It has the effect of improving corrosion resistance by suppressing the precipitation of Cr carbide. The lower limit of Nb is set to 0.1% by mass from the amount necessary for fixing C and N in order to prevent intergranular corrosion. On the other hand, if the content of Nb is too high, the hot cracking resistance at the time of welding and brazing decreases and the toughness is impaired, so 0.6 mass% is made the upper limit.

Cu has an effect of improving the corrosion resistance by stabilizing the passive film by reducing the anode current. In order to obtain a stable corrosion resistance improving effect, the lower limit is set to 0.1% by mass. Excessive addition lowers the workability and also reduces the corrosion resistance, so 1.0 mass% is made the upper limit.

  Mo is generally well known for its action to increase the corrosion resistance of stainless steel in the presence of Cr. For this reason, in this invention, Mo can be added as needed. As a result of various studies, it is more effective to secure a Mo content of 0.3% by mass in order to sufficiently exhibit the effect of enhancing the corrosion resistance of stainless steel by Mo. However, excessive addition of Mo causes a decrease in workability and an increase in cost. Therefore, when adding Mo, it is performed in a range of less than 6.0% by mass.

Example 1
Using the ferritic stainless steel of the present invention 1 shown in Table 1 as a material, a large chemical tank 1 having the structure shown in FIG. 1 was manufactured. The members manufactured using the ferritic stainless steel according to the first aspect of the present invention are the cylindrical body 5, the hemispherical bottom plate 6, the lid 3, and the pipe 4 among the pipe members 12.

The large tank 1 for chemical liquid has an outer diameter of 600 mm and a height of 1200 mm. The main body member 2 and the lid 3 have a plate thickness of 2 mm, and the pipe 4 is a TIG welded pipe having an outer diameter of 20 mm and a plate thickness of 1.5 mm. As the upper flange 8 and the lower flange 11, those having a plate thickness of 4 mm and an outer diameter of 60 mm were used.

The cylindrical body portion 5 of the main body member 2 was bent so as to have an outer diameter of 600 mm, the ends were joined by TIG welding, and the outward curled portion 14 having an outer diameter of 20 mm was processed at the lowermost end.
The hemispherical bottom surface 6 was processed into a hemispherical shape having a radius of curvature of 800 mm. The lid 3 was provided with a burring portion having a hole diameter of 25 mm and a height of 20 mm in the center, and the lower flange 11 was disposed on the burring portion and joined by TIG welding.
The cylindrical body 5 and the hemispherical bottom surface 6 were joined by seam welding at a position where the length of the lower region 13 was 60 mm. The cylindrical body 5 and the lid 3 were joined by seam welding at a position 50 mm from the top of the cylindrical body 5 so that the pipe 12 was surrounded by the cylindrical body 5.
Seam welding was performed using a pair of chromium-copper electrode wheels with an outer diameter of 150 mm, a width of 10 mm, and a radius of curvature of 40 mm at the tip, with a pressure of 3 kN, a welding current of 10 kA, and a welding speed of 2 m / min.
On the other hand, the pipe member 12 was manufactured by forming a through hole in the center of the upper flange 8 and sealing the periphery of the pipe through the pipe 4 by TIG welding.
The upper flange 8 was provided with six holes of 9 mm for passing the bolts 10 and the lower flange 11 was provided with six M6 female screw portions.
Subsequently, a sealing material 9 was prepared. The sealing material 9 is made of polypropylene having an outer diameter of 60 mm and a thickness of 2 mm, and has one hole with a diameter of 30 mm for allowing the pipe 4 to pass through the center, and six bolt holes with a diameter of 9 mm in the same arrangement as the bolt bolt holes on the periphery. It is what opened. The sealing material 9 is placed on the lower flange 11, the pipe 4 of the pipe member 12 is inserted into the main body member from the insertion port 7 of the main body member 2, and the upper flange 8 and the lower flange 11 are fastened with bolts 10. A large tank 1 for chemicals was completed.
(Example 2)

Using the ferritic stainless steel of the present invention 2 shown in Table 1 as a raw material, the large-sized chemical tank 1 shown in FIG. 1 was manufactured. The dimensions of each part of the large chemical liquid tank 1, the welding method, and the specifications of the sealing material 9 were the same as those in Example 1.
(Comparative Example 1)

Using SUS304 shown in Table 1 as a raw material, the large tank 1 for chemical solution shown in FIG. 1 was manufactured. The chemical large tank 1 was manufactured in the same manner as in Example 1 except that the dimensions and welding methods of the chemical liquid large tank 1 and the specifications of the sealing material 9 were set to a welding current of 8 kA.
(Comparative Example 2)

The same large chemical tank 1 as in Example 1 was manufactured except that the curled portion 14 at the lower end of the cylindrical body portion was wound inward from the large chemical liquid tank 1 shown in FIG.
(Comparative Example 3)
Using the ferritic stainless steel of the present invention 1 shown in Table 1 as a raw material, the large-sized chemical tank 1 shown in FIG. 1 was manufactured. The dimensions of each part of the large chemical tank 1 and the specifications of the sealing material 9 are the same as those in the first embodiment. However, the cylindrical body 5 and the hemispherical bottom surface 6 are joined together, and the cylindrical body 5 and the lid 3. Both were joined by TIG welding. The TIG welding conditions were such that the welding current was 120 A, the welding speed was 0.3 m / min, and the shielding gas was Ar gas. After welding, grinder polishing was performed with a grindstone of the raised weld bead.

  200 liters of lithium hexafluorophosphate was injected into the large chemical tank 1 shown in Examples 1 and 2 and Comparative Example 1, and the tank body was tilted 45 degrees assuming a drop during loading and unloading work from the truck bed. In this state, it was dropped freely from a height of 1.5 m in the vertical direction. As a result, it was found that cracks occurred in the body member 2 at a gap height of 20 mm in any material, but no cracks occurred at a gap height of 40 mm, and the material sufficiently resisted the impact force. In addition, 200 liters of lithium hexafluorophosphate was also injected into the large chemical liquid tank 1 shown in Comparative Example 2 and allowed to fall freely under the same test conditions as above, but the curled portion 15 was opened and the lower cylindrical member was opened. 14 deformed, and the main body member 2 was cracked.

  200 liters of a lithium ion battery electrolyte solution based on lithium hexafluorophosphate was injected into the large chemical solution tanks 1 of Examples 1 and 2 and Comparative Examples 1 to 3, and left in a 90 ° C. atmosphere for one month. The state of the large chemical tank 1 was evaluated. As a result of evaluation, no abnormalities such as deformation and liquid leakage were found in the large chemical tank 1 of Example 1 and Comparative Examples 1 and 2, but in the large chemical tank 1 of Comparative Example 3, In addition, the weld bead polishing amount was excessive and the thickness of the joint became thin, and the thin joint became deformed by the expansion of the electrolyte.

  The large tank for chemical liquid according to the present invention is suitable in terms of production and cost as a tank for storing and transporting chemical liquid.

DESCRIPTION OF SYMBOLS 1 Large chemical tank 2 Main body member 3 Lid 4 Pipe 5 Cylindrical trunk | drum 6 Bottom face 7 Insertion port 8 Upper flange 9 Sealing material 10 Bolt 11 Lower flange 12 Pipe member 13 Lower region 14 Curled part 15 Welded part

Claims (5)

A large tank for a chemical solution having a main body member composed of a cylindrical member, a bottom plate bonded to the lower portion thereof, and a lid bonded to the upper portion of the cylindrical member,
The lower end of the cylindrical member has an outward curl shape,
A large tank for a chemical solution, characterized in that both the joining of the cylindrical member and the bottom plate and the joining of the cylindrical member and the lid are seam welding.   The large tank for a chemical solution according to claim 1, wherein the bottom plate has a hemispherical shape that protrudes downward.   The large tank for chemical | medical solutions of Claim 1 or 2 provided with the pipe member which inject | pours / discharges a chemical | medical solution in the said main body member.   4. The ferritic stainless steel to which Mo is added in an amount of 0.3% by mass or more and Nb is added in an amount of 0.1% by mass or more is used as a material for the main body member and the pipe member. Large tank for chemicals described. The large tank for chemical | medical solution in any one of Claim 1 to 3 which used the ferritic stainless steel which added 0.1 mass% or more of Cu and Nb for the raw material of a main body member and a pipe member, respectively.

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